Round-the-clock cleanup efforts were required in Menomonie, Wisconsin, due to a fatal crash of a semi-trailer truck that drove off Interstate 94 and plunged into the icy river beneath the Red Cedar River Bridge.

The semi was loaded with 23,800 pounds of Scott’s lawn fertilizer that contains the herbicide HALTS, which inhibits the growth of crabgrass. Many of the 40-pound bags of phosphorus-free fertilizer broke open when the rig hit the ice.

Divers happy to find fish still alive brought up 80 saturated bags of fertilizer to the surface by hand. A total of 209 bags were recovered.

“The cleanup has been fraught with difficulty,” said Tom Kendzierski, Department of Natural Resources spill coordinator. “The material lies below the broken ice sheet in 25 feet of water at the base of steeply sloping stream banks.” Due to the crash site location, it was also difficult to access it with heavy equipment on barges.

A crane was used to lift fertilizer bags and other debris from the area so it could be hauled away. Attempts to remove the contaminated ice proved to be unsuccessful. But crews were able to corral the floating fertilizer within containment booms. This is because HALT doesn’t mix well with water; it floats. A vacuum truck was also used to collect diesel and herbicide from the water’s surface and crews put absorbent pads into place.

Crews will continue for weeks to remove the herbicide as it floats to the surface and the ice breaks up. An additional boom will be put in place below the spill site to harness any remaining contaminants on the water’s surface. “Timing for the cleanup is critical because spring runoff is likely to occur in the near future, with increased volumes of water, swifter currents and the break up and movement of river ice,” said Kendzierski.